With development of the mobile Internet and popularization of intelligent terminals, data traffic increases rapidly. A wireless local area network (WLAN) becomes one of mainstream mobile broadband access technologies by virtue of advantages of a high rate and low costs.
To significantly improve a service transmission rate of a WLAN system, the next-generation Institute of Electrical and Electronics Engineers (IEEE) 802.11ax standard further uses an Orthogonal Frequency Division Multiple Access (OFDMA) technology on a basis of an existing Orthogonal Frequency Division Multiplexing (OFDM) technology. The OFDMA technology divides time-frequency resources of a wireless channel of an air interface into multiple orthogonal time-frequency resource units (RB, Resource Block). The RBs are shared in terms of time and are orthogonal in terms of a frequency field. In 802.11ax, a transmission bandwidth allocated to users is referred to as a resource unit, and therefore, is only represented by “resource unit” subsequently.